There is still one race up in the air between two Democrats in the state's primaries. Dan Koh and Lori Trahan are vying for the 3rd Congressional District seat, to succeed retiring congresswoman Niki Tsongas. The Associated Press says that as of late this afternoon, just 52 votes are separating Trahan and Koh, with Trahan in the lead. As such, the race could be headed for a recount. John Cluverius is an assistant professor of political science at UMass Lowell. He spoke with WGBH All Things Considered anchor Barbara Howard about what a recount would look like.

The following transcript has been edited for clarity.

Barbara Howard: So it was a crowded field in the 3rd District. 10 candidates were on the ballot, but now it's come down to Trahan, who was chief of staff to former Massachusetts congressman Marty Meehan, and Dan Koh, the former chief of staff to Boston mayor Marty Walsh. Trahan declared victory last night not too long after the polls closed. And here she was again earlier today:

Sound from Lori Trahan: Now that 100 percent of the votes have been counted, I'm confident that I am your Democratic nominee.

Howard: So there were 100 percent of the precincts reporting, and as of right now, each candidate has about 21.6 percent of the votes. Is she being premature in making a declaration like that, or is it a strategic move on her part?

John Cluverius: It's absolutely a strategic move on her part. The person who is ahead at any point in the race, especially when we have a sort of rough unofficial total, should obviously, I think, declare themselves the winner. That's in their strategic interest because they want to be able to fundraise for the general election, fundraise for any potential recount. And declaring victory last night has the advantage of putting her opponent on the defensive and also implying to reporters, to the public, and to her opponent that in the course of election night, she knew something that they did not.

Howard: Now Koh, her opponent, is saying not so fast to that victory speech. You spoke about money being needed to do a recount. Who pays for a recount?

Cluverius: In Massachusetts, recounts are free and paid for by the state as long as the margin of victory is less than half of 1 percent. But there may be additional costs that aren't borne by the counting of votes, but rather maintaining staff and a legal team to ensure that the vote is counted as a candidate would perceive to be fair.

Howard: So how does a recount actually work? What physically has to happen?

Cluverius: The recount is actually a relatively simple process. They go through totals from various machines, absentee, provisional, and paper ballots, and simply ensure that those ballot totals match the count that they have.

Howard: At this point, the ballots themselves - where physically are they? I understand that they're sealed? Is that the Massachusetts Secretary of State's office that oversees that?

Cluverius: Yeah, the Secretary of State's office can order that the ballots be sealed. It essentially serves to prevent anyone from accessing the ballots.

Howard: How long does a recount take to perform?

Cluverius: Usually a recount only takes about a day.

Howard: OK. Thanks for joining us, Professor Cluverius.

Cluverius: It's my pleasure. Thank you so much.

Howard: That's John Cluverius, assistant professor of political science at UMass Lowell, speaking with us about the race in Massachusetts’ 3rd Congressional District between Lori Trahan and Dan Koh. Those two candidates emerged from a field of 10 last night. Trahan leads Koh by just 52 votes, according to the Associated Press. The candidates have until Friday to take steps to initiate a recount, according to the office of Massachusetts Secretary of State Bill Galvin.